A. In subjects without known organic heart disease, ventricular arrhythmias precipitated by exercise or occurring during routine activity increase in frequency and complexity with age and cause substantial cardiac morbidity. Although increased echocardiographic left ventricular (LV) mass predicts a higher prevalence and complexity of ventricular arrhythmias (VA) on ambulatory ECG, whether such a relationship between LV anatomy and exercise-induced VA (EIVA) is unknown. We therefore examined this question in 288 healthy BLSA volunteers 20-90 years old who underwent both M-mode echocardiography and maximal treadmill exercise testing. Simple, i.e. isolated, EIVA occurred in 53 subjects (18%) and complex EIVA (comparing greater than or equal to 10% of beats in any minute or occurring in runs) in 15 subjects (5%). Although univariate predictors of any EIVA were greater LV mass (p=.0006), older age (=.0009), larger body surface area (p=.003), higher peak systolic blood pressure (p=.01) and male sex (p=.01), only age (p=.002) independently predicted. EIVA by multiple logistic regression analysis. B. Although respiratory sinus arrhythmias (RSA) is known to decrease with advancing age, the independent effects of age, gender, conditioning status and body composition are unknown. The impact of age, fitness, gender and relative weight on resting heart rate variability was examined in 117 healthy normotensive adults ages 19-82 from the BLSA; heart rate variability was indexed by RSA, extracted from a 3-minute seated ECG using time domain digital filtering. By linear regression analysis, RSA varied inversely with age (r = -0.61, p less than .001) and body mass index (r = -0.31, p less than .01), directly with VO2max (r = 0.40, p less than .001) and was unrelated to gender. Multiple regression analysis demonstrated that age and body mass but not VO2max were independent predictors of RSA. C. To examine the hypothesis that heart rate variability (HRV) is reduced in apparently healthy subjects with latent coronary artery disease (CAD), we measured resting ECG R-R interval variations in 29 asymptomatic male volunteers aged 61.8 +/- 11.2 years, free of clinical heart disease, who developed a coronary event (CE), within the next 2 years. Compared to 58 age-matched controls (C) who remained event free for 12.7+/-6.5 years after the index ECG, men destined for a CE showed smaller standard deviation of R-R (26.1 +/- 10.8 vs 37.9 +/- 24.0 msec, p = .002) and smaller absolute difference between minimum and maximum R-R (98.6 +/- 40.3 vs 136.7 +/- 81.0 msec, p = .004) indicating reduced HRV in men with latent CAD.